PhD progress after 2 yearsconference2015.redmud.org/wp-content/uploads/2015/10/P5... ·...
Transcript of PhD progress after 2 yearsconference2015.redmud.org/wp-content/uploads/2015/10/P5... ·...
PhD progress after 2 years
Recovery of scandium from leachates of Greek bauxite residue by adsorption on
functionalized chitosan-silica hybrid materials
Presentation for the VITO doctorate jury
by Joris Roosen
29-10-2015
CONTENT
• Project outline• Valorization of bauxite residue• Approach
❶ INTRODUCTION
• Synthesis of functionalized, hybrid materials• Leaching of bauxite residue• Selectivity by pH variation
❷ PREPARATION
• Kinetics of Sc(III) adsorption• Selectivity by functional group• Reusability study
❸ BATCH ADSORPTION
• Principle of ion-exchange column chromatography• Scandium separation experiment❹ COLUMN SEPARATION
2
Use of biomaterialsfor selective adsorption
* Chitosan from seafood waste* Alginate from brown algae
3
❶ Introduction❷ Preparation❸ Batch adsorption❹ Column separation
• PROJECT OUTLINE• Valorization of bauxite residue• Approach
Evolution towards ... ... a sustainable future!
Valorization of waste streamsby recovery of critical metals
* Rare-earth elements* Gallium and indium
Green applications
4
❶ Introduction❷ Preparation❸ Batch adsorption❹ Column separation
• Project outline• VALORIZATION OF BAUXITE RESIDUE• Approach
• Production rate of bauxite residue = 120 million tons per year, with currently no large-scaleindustrial applications large amounts have been stockpiled already
• “The” solution to the red mud problem should consist of a combination of applications in different fields (iron & steel, building & construction, REE, …)
• Inclusion of critical metal recovery in the flow sheet of alumina refineries could help1) to guarantee a stable supply of these critical metals2) to meet the high processing/disposal costs of bauxite residue
• 90% of the economical value of bauxite residue arises from the presence of scandiumo Price of Sc2O3 (99.99%) > 5000 US$/kg (2013)o Upcoming market because of promising applications (Al-Sc alloys, SOFC’s, …)
• Promising trials already showed that ion-exchange adsorption is the most suitable techniqueto recover small amounts of valuable elements from high amounts of diluted waste streams
5
❶ Introduction❷ Preparation❸ Batch adsorption❹ Column separation
• Project outline• Valorization of bauxite residue• APPROACH
❶ Biosorbent hybridization with silica
• Hybridization of chitosan and silica results in a superior material with combined benefits:high adsorption capacity, porosity, stability and chemical (acid) resistance
• The material becomes industrially applicable in chromatography set-ups
❷ Immobilization of proper functional groups
• Sorbent selectivity can be improved by easy functionalization on chitosan NH2 groups
• Affinity of a certain organic group for specific metal ions can be predicted by considering thecorresponding stability constants between free ligand and metal ion:
log K values Sc(III) Fe(III) Nd(III)
IDA 9.9 11.1 6.5
NTA 12.70 15.87 11.26
DTPA 26.3 27.3 21.6
EGTA 25.4 20.5 16.3
6
❶ Introduction❷ Preparation❸ Batch adsorption❹ Column separation
• SYNTHESIS OF FUNCTIONALIZED, HYBRID MATERIALS• Leaching of bauxite residue• Selectivity by pH variation
❶ Hybridization of chitosan with silica by sol-gel chemistry
TEOS
❷ Functionalization by immobilization of organic ligands (via formation of a stable amide bond)
7
❶ Introduction❷ Preparation❸ Batch adsorption❹ Column separation
• Synthesis of functionalized, hybrid materials• LEACHING OF BAUXITE RESIDUE• Selectivity by pH variation
• Greek bauxite residue (AoG)
• Leaching was done with a 0.20 M HNO3 solution (L:S ratio = 50:1)
constant agitation for 24 h at 160 rpm and 25 °C
• Leachates were filtrated to remove solid particles
• Composition of the leachates:
Fe 106 ppm Sc 2.1 ppm
Al 670 ppm Y 0.4 ppm
Na 1104 ppm La 0.6 ppm
Ca 939 ppm Nd 0.8 ppm
Si 558 ppm Dy 0.1 ppm
Ti 106 ppm Σ Ln 6.0 ppm
8
❶ Introduction❷ Preparation❸ Batch adsorption❹ Column separation
• Synthesis of functionalized, hybrid materials• Leaching of bauxite residue• SELECTIVITY BY pH VARIATION
0 1 2 3 4 5
0
20
40
60
80
100
Sc(III) precipitation
Fe(III) precipitation Fe(III) Sc(III)
Amou
nt o
f pre
cipita
tion
(%)
Equilibrium pH
Investigation of Fe(OH)3 and Sc(OH)3 precipitation as a consequence of hydrolysis.Experimental conditions: V = 10.0 mL, ci = 0.50 mM.
Co-precipitation of Sc(III) withFe(III) is observed in a binary,
equimolar solution of Fe(III) andSc(III) with increasing pH
↓
Not possible to separate Fe(III) and Sc(III) by variation of the pH, certainly not at higher (relative)
concentrations of Fe(III)
❶ Introduction❷ Preparation❸ Batch adsorption❹ Column separation
• KINETICS OF Sc(III) ADSORPTION• Selectivity by functional group• Reusability study
0 50 100 150 200 250 300 350 400
0.00
0.05
0.10
0.15
0.20
DTPA-chitosan-silica EGTA-chitosan-silica
Adso
rptio
n am
ount
(mm
ol g
-1)
Contact time (min)
0
20
40
60
80
100
Met
al io
n re
cove
ry (%
)
9
10
0 1 2 3 4
0
20
40
60
80
100
Fe(III) removed Sc(III) removed
Met
al io
n re
mov
al (%
)Equilibrium pH
(b)
DTPA-chitosan-silica EGTA-chitosan-silica
Functionalization with two different organic ligands opposite affinities in single-element solutions of Sc(III)/Fe(III) as a consequence of different stability constants selectivity
observed for Sc(III) with EGTA-chitosan-silica in an equimolar, binary solution of Fe(III) and Sc(III)
❶ Introduction❷ Preparation❸ Batch adsorption❹ Column separation
• Kinetics of Sc(III) adsorption• SELECTIVITY BY FUNCTIONAL GROUP• Reusability study
0 1 2 3 4
0
20
40
60
80
100
Fe(III) removed Sc(III) removed
Met
al io
n re
mov
al (%
)
Equilibrium pH
(a)
11
❶ Introduction❷ Preparation❸ Batch adsorption❹ Column separation
• Kinetics of Sc(III) adsorption• Selectivity by functional group• REUSABILITY STUDY
1 2 3 4 5 6 7
0
20
40
60
80
100
Adso
rptio
n ef
ficien
cy (%
)
Cycle number
Reusability of EGTA-chitosan-silica. Adsorption from an aqueous solution of Sc(NO3)3. Stripping with 1.0 M HNO3 (10 mL). Experimental conditions: mads = 25.0 mg; V = 10 mL; ci = 0.50 mM;
adsorption time = 4 h; stripping time = 1 h.
12
❶ Introduction❷ Preparation❸ Batch adsorption❹ Column separation
• PRINCIPLE OF ION-EXCHANGE COLUMN CHROMATOGRAPHY• Scandium separation experiment
Chelating ion exchange: formation of a coordinate bond between the metal cation and the surface functional group
Selectivity depends on ≠ in stability constants
A higher affinity for the resin results in slower migration through the colum
Breakthrough of the different elements in theleachate is initiated by applying a decreasing pH gradient with diluted solutions of HNO3.
13
0 50 100 150 200 250
0
20
40
60
80
100
Cum
ulat
ive m
etal
per
cent
age
(%)
Elution volume (mL)
Na Ca Al Σ Ln Fe Ti Si Sc
0.0
0.5
1.0
1.5
2.0
2.5
pH
• Principle of ion-exchange column chromatography• SCANDIUM SEPARATION EXPERIMENT
❶ Introduction❷ Preparation❸ Batch adsorption❹ Column separation
Optimized isolation of scandium from a bauxite residue leachate by ion-exchange column chromatography with EGTA-chitosan-silica as resin material and a decreasing pH gradient.
14
CONCLUSIONS
• Metal-ion recovery is considered as an important aspect in the valorization of bauxiteresidue, in order to solve the red mud problem in combination with applications in otherfields.
• Functionalization of chitosan-silica particles with EGTA-groups resulted in a hybrid material with a remarkably high adsorption affinity for scandium, higher than that of a similar hybrid material, functionalized with DTPA-groups.
• A high selectivity was observed compared to the other components (mainly iron, titanium and silicon) present in a HNO3 leachate of Greek bauxite residue.
• Scandium was isolated from the other elements by ion-exchange column chromatography, by applying a decreasing pH gradient with aqueous solutions of HNO3. Scandium broke through the column at a pH of 0.50, a much lower value than the ones observed for the other metal ions present in the leachate.
THANK YOU… … for your attention!
Other workRoosen, J., Spooren, J., Binnemans, K., Adsorption performance of functionalized chitosan-silica hybrid materials toward rare earths. Journal of Materials Chemistry A, 2014, vol. 2, p. 19415-19426
Acknowledgement• Promotor Prof. Dr. Koen Binnemans (KU Leuven)
• Co-promotor Dr. Steven Mullens (VITO)
• Drs. Stijn Van Roosendael (thesis student)
• Drs. Chenna Rao Borra (leaching work)
• Aluminium of Greece (bauxite residue sample)
Financial support
• FWO
• VITO
• KU Leuven
15
Questions